The ocean is one of the most attractive and less explored ecosystems on the planet. Above, at a depth of 200 to 1,000 meters, is the Mesopelogic or Twilight Zone, where only a small amount of sunlight reaches. It is home to three species of sharks that are capable of emitting light in the dark. A team of scientists from the Catholic University of Louvain (Belgium) visited New Zealand in January 2020 and spent a month at sea studying the noisy rice sharks off the east coast of the country. Jerome Mallefet, The leader of the expedition, devoted his entire life to studying these fish and believes that 11% of the known shark species are biologically glowing. His trip to New Zealand has allowed the scientific community to prove it with these three creatures, in a study published in the journal Boundaries in marine science.
Mallefet was able to capture specimens from three different families: black belly light shark (Edmopterus Lucifer), Southern Light Shark (Edmopterus granulosusAnd kite or karaoke shark (Taladias though) He transferred them to the water tank in a dark room on the ship, where his team was able to photograph the animals emitting spectacular blue-green light. “It is my dream to see Taladias though Shined, because no one in the world has ever seen it, and I firmly believe that it is the largest bioluminescent shark ever known, ”explains Mallefet about the carousel shark, which reaches 180 cm and, thanks to this discovery, is the largest luminous spine in the world.
Bioluminescent animals contain light-producing elements, photophores. In most of them this process is controlled by the nervous system. But when a team of Belgian scientists studied the skin of the skin Sharks Captured, he was surprised to find that where photophores are found, light production is the only animal that is regulated by hormones. “Because all the nerve transmitters failed, it took us a whole year to figure out how to trigger the element of light,” says Mallefet. Until they realized that the same hormone that induces sleep in humans is melatonin, the stimulus of light in sharks was: “Melatonin stimulates the production of light and the hormone alpha-MSH stops it. It is a very slow process.”
The light produced by these sharks helps to obscure their shadow and does not warn other predators of their presence.
The researchers’ next step is to find out why sharks emit light. Mallefet is the most plausible hypothesis that it is a camouflage technique to live in an area. The sea Where there is not much room to hide: “Such a small shark can be eaten by any large fish or other shark. If the shadow also produces blue light, the two lights are mixed.The hypothesis of the opposite shade is that it disappears and shines and is not eaten by predators.
The Belgian team’s voyage on New Zealand waters was thanked by NIWA, the country’s national maritime and atmospheric research institute. Darren Stevens He was the professional fisheries scientist in charge of the ship. In his life he caught many unusual fish (including two giant squid) but he never expected the sharks he constantly sees to glow in the dark. “We saw light-emitting bacteria and algae. We caught bioluminescent ink-emitting squid, many small fish that live in the twilight zone, just like the standard light fish, of course the valley fish. I have seen, but I never imagined that some large sharks can do this.If you think of the stone shark that weighs between 1.8 meters and 30 kg, it is incredible to find that they are large and impressive animals that can communicate with living light.
Stevens acknowledges the discovery by Belgian researcher Jerome Mallefet Sharks This will help to understand the role of bioluminescence in the ocean. In the animal kingdom, 80% of bioluminescence is found in the oceans, and only light-producing vertebrates live in salt water. “5% of the oceans are the surface of the ocean and the remaining 95% is the ocean floor, which is the largest habitat in the world and we know nothing about it,” Mallefet says with a broad smile as he participates in another sea voyage once the epidemic is under control. His dream was to continue exploring the darker parts of the ocean and, as he believed, to discover whether bioluminescence was a form of communication for those who lived in the depths.
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